In a rotary machine such as a turbine, a seal device is used for suppressing leakage of gas from the high pressure side to the low pressure side along the circumference of a rotor. It is desired that a seal follows variations of a clearance between a stator and the rotor of the rotary machine and eccentricity between the stator and the rotor and exerts sealing performance. From such a viewpoint, a brush seal in which bundled wire rods are fixed to a metal plate is adopted in place of a labyrinth seal. In order to simplify tasks of attaching and detaching the brush seal to the rotary machine, a split type brush seal device in which a brush seal is divided into arc brush seal pieces and plural brush seal pieces are placed side by side in the circumferential direction is proposed (for example, refer to Patent Literatures 1, 2).